1. Field of the Invention
The present invention relates to a light quantity measuring device and a method for measuring light quantity that measure a incident light quantity.
2. Description of the Related Art
In recent years, light quantity measuring devices that measure light quantities, of ultraviolet radiation and the like included in sunlight and the like, have become widespread.
FIG. 7 shows an example of an electrical structure of a conventional light quantity measuring device 10′.
The light quantity measuring device 10′ includes a light reception element 50′ that outputs a signal representing a quantity of light incident on a light reception surface. The signal outputted by the light reception element 50′ is converted to a voltage by a converter 52′, the voltage converted by the converter 52′ is converted to a digital signal by an analog/digital conversion circuit (hereinafter referred to as an ADC) 72′, the incident light quantity on a light reception surface 60 is calculated from the digital signal by a CPU 70′, and information representing the calculated light quantity is displayed at a display section 16′.
However, as a position of the sun changes with time, an incident angle of incident light with respect to a light reception portion 12′ shifts from a direction at which the quantity of incident light is at a maximum (for example, a direction in which the light is incident at 90° with respect to the reception surface). As a result, with such a device, received light quantities according to the light reception element are decreased relative to actual light quantities, by quantities corresponding to the shifting.
Japanese Patent Application Laid Open (JP-A) No. 2000-121430 has disclosed a technology which is: a retainer including a support pedestal that retains the light quantity measuring device; a fixed platform that axially supports the support pedestal to be rotatable; and a base to which the fixed platform is fixed. By the support pedestal that retains the light quantity measuring device being turned, the light reception surface of the light quantity measuring device is oriented to 90° with respect to the sun.
However, it is necessary for an operator him/herself to adjust the incident angle of incident light on the light reception surface of the light quantity measuring device.